Support material formulation and additive manufacturing processes employing same

ABSTRACT

Novel support material formulations, characterized as providing a cured support material which is readily removable by contacting with water, are disclosed. The formulations comprise a curable water-soluble mono-functional monomer, a water-miscible polymer and a silicone polyether. Methods of fabricating a three-dimensional object, and a three-dimensional object fabricated thereby are also disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/557,137 filed on Sep. 11, 2017, which is a National Phase of PCTPatent Application No. PCT/IL2016/050264 having International FilingDate of Mar. 10, 2016, which claims the benefit of priority under 35 USC§ 119(e) of U.S. Provisional Patent Application No. 62/131,338 filed onMar. 11, 2015. The contents of the above applications are allincorporated by reference as if fully set forth herein in theirentirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to additivemanufacturing (AM), and more particularly, but not exclusively, toformulations useful for forming a support material in additivemanufacturing such as three-dimensional inkjet printing, and to methodsof additive manufacturing utilizing same.

Additive manufacturing (AM) is a technology enabling fabrication ofarbitrarily shaped structures directly from computer data via additiveformation steps (additive manufacturing; AM). The basic operation of anyAM system consists of slicing a three-dimensional computer model intothin cross sections, translating the result into two-dimensionalposition data and feeding the data to control equipment which fabricatesa three-dimensional structure in a layerwise manner.

Additive manufacturing entails many different approaches to the methodof fabrication, including three-dimensional printing such as 3D inkjetprinting, electron beam melting, stereolithography, selective lasersintering, laminated object manufacturing, fused deposition modeling andothers.

Three-dimensional (3D) printing processes, for example, 3D inkjetprinting, are being performed by a layer by layer inkjet deposition ofbuilding materials. Thus, a building material is dispensed from adispensing head having a set of nozzles to deposit layers on asupporting structure. Depending on the building material, the layers maythen be cured or solidified using a suitable device.

Various three-dimensional printing techniques exist and are disclosedin, e.g., U.S. Pat. Nos. 6,259,962, 6,569,373, 6,658,314, 6,850,334,6,863,859, 7,183,335, 7,209,797, 7,225,045, 7,300,619, and 7,500,846 andU.S. Patent Application having Publication No. 20130073068, all by thesame Assignee.

During the additive manufacturing (AM) process, the building materialmay include “model material” (also known as “object material” or“modeling material”), which is deposited to produce the desired object,and frequently, another material (“support material” or “supportingmaterial”) is used to provide temporary support to the object as it isbeing built. The other material is referred to herein and in the art as“support material” or “supporting material”, and is used to supportspecific areas of the object during building and for assuring adequatevertical placement of subsequent object layers. For example, in caseswhere objects include overhanging features or shapes, e.g. curvedgeometries, negative angles, voids, and the like, objects are typicallyconstructed using adjacent support constructions, which are used duringthe printing and then subsequently removed in order to reveal the finalshape of the fabricated object.

The modeling material and the supporting material may be initiallyliquid and subsequently hardened to form the required layer shape. Thehardening process may be performed by a variety of methods, such as UVcuring, phase change, crystallization, drying, etc. In all cases, thesupport material is deposited in proximity of the modeling material,enabling the formation of complex object geometries and filling ofobject voids. In such cases, the removal of the hardened supportmaterial is liable to be difficult and time consuming, and may damagethe formed object.

When using currently available commercial print heads, such as ink-jetprinting heads, the support material should have a relatively lowviscosity (about 10-20 cPs) at the working, i.e., jetting, temperature,such that it can be jetted. Further, the support material should hardenrapidly in order to allow building of subsequent layers. Additionally,the hardened support material should have sufficient mechanical strengthfor holding the model material in place, and low distortion for avoidinggeometrical defects.

Examples of materials that can be used as supporting materials are phasechange materials, with wax being a non-limiting example. At anappropriately high temperature these materials melt and thus permitsupport removal when in the liquid state. One of the drawbacks of suchphase change is that the temperature required for melting the supportingmaterial may also cause deformation of the model, and hence of theobject structure.

Known methods for removal of support materials include mechanical impact(applied by a tool or water-jet), as well as chemical methods, such asdissolution in a solvent, with or without heating. The mechanicalmethods, however, are labor intensive and are unsuited for smallintricate parts.

For dissolving the support materials, the fabricated object is oftenimmersed in water or in a solvent that is capable of dissolving thesupport materials. In many cases, however, the support removal processmay involve hazardous materials, manual labor and/or special equipmentrequiring trained personnel, protective clothing and expensive wastedisposal. In addition, the dissolution process is usually limited bydiffusion kinetics and may require very long periods of time, especiallywhen the support constructions are large and bulky. Furthermore,post-processing may be necessary to remove traces of a ‘mix layer’ onobject surfaces. The term “mix layer” refers to a residual layer ofmixed hardened model and support materials formed at the interfacebetween the two materials on the surfaces of the object beingfabricated, by model and support materials mixing into each other at theinterface between them.

Additionally, methods requiring high temperatures during support removalmay be problematic since there are model materials that aretemperature-sensitive, such as waxes and certain flexible materials.Both mechanical and dissolution methods for removal of support materialsare especially problematic for use in an office environment, whereease-of-use, cleanliness and environmental safety are majorconsiderations.

Water-soluble materials for 3D building have been previously described.For example, U.S. Pat. No. 6,228,923 describes a water solublethermoplastic polymer—Poly(2-ethyl-2-oxazoline)—for use as a supportmaterial in a 3D building process involving high pressure and hightemperature extrusion of ribbons of selected materials onto a plate.

A water-containing support material comprising a fusible crystal hydrateis described in U.S. Pat. No. 7,255,825. Fusible crystal hydratesundergo a phase change from solid to liquid (i.e. melt) usually athigher than ambient temperature (typically between 20° C. and 120° C.depending upon the substance). Typically, upon melting, fusible crystalhydrates turn into aqueous solutions of the salts from which they areformed. The water content in these solutions is typically high enough tomake the solutions suitable for jetting from a thermal ink-jetprinthead. The melting process is reversible and material dispensed in aliquid state readily solidifies upon cooling.

Water-soluble compositions suitable for support in building a 3D objectare described, for example, in U.S. Pat. Nos. 7,479,510, 7,183,335 and6,569,373, all to the present Assignee. Generally, the compositionsdisclosed in these patents comprise at least one UV curable (reactive)component, e.g., an acrylic component, at least one non-UV curablecomponent, e.g. a polyol or glycol component, and a photoinitiator.After irradiation, these compositions provide a semi-solid or gel-likematerial capable of dissolving or swelling upon exposure to water, to analkaline or acidic solution or to a water detergent solution.

Besides swelling, another characteristic of such a support material maybe the ability to break down during exposure to water, to an alkaline oracidic solution or to a water detergent solution because the supportmaterial is made of hydrophilic components. During the swelling process,internal forces cause fractures and breakdown of the cured support. Inaddition, the support material can contain a substance that liberatesbubbles upon exposure to water, e.g. sodium bicarbonate, whichtransforms into CO₂ when in contact with an acidic solution. The bubblesaid in the process of removal of support from the model.

SUMMARY OF THE INVENTION

There is an unmet need for improved support materials in 3D inkjetprinting.

The present inventors have now designed and successfully practiced novelwater-soluble support material formulations, which supersede currentlyknown support material formulations. The hardened (e.g., cured) supportmaterial obtained upon dispensing and curing these formulations caneasily and efficiently be removed by dissolution in water or an aqueoussolution, without excessive use of harsh chemical reagents, and/orwithout adversely affecting mechanical properties of the object.

The support material formulations described herein include a curablemono-functional monomer, a non-curable water-miscible polymer and asilicon polyether substance, and optionally also surface active agents,initiators, inhibitors, and the like.

According to an aspect of some embodiments of the present inventionthere is provided a support material formulation comprising a curable,water-soluble mono-functional monomeric material; a non-curablewater-miscible polymeric material; and a silicone polyether.

According to some of any of the embodiments of the present invention,the water-miscible polymeric material comprises a polyol.

According to some of any of the embodiments of the present invention,the polyol is selected from the group consisting of Polyol 3165,polypropylene glycol, and polyglycerol.

According to some of any of the embodiments of the present invention,the silicone polyether is represented by Formula I:

wherein:

n and m are each independently an integer, wherein n+m is an integer offrom 1 to 500, representing the number of backbone units, minus 1;

X is an alkylene or absent;

Y is a polyether moiety or absent; and

A and B are each independently an alkyl or a polyether moiety,

provided that either Y or each of A and B is the polyether moiety.

According to some of any of the embodiments of the present invention,the polyether moiety is represented by Formula II:—O—[(CR′R″)x-O]y-Z   Formula II

wherein:

y is an integer of from 4 to 100;

x is an integer of from 2 to 6;

R′ and R″ are each independently hydrogen, alkyl, cycloalkyl, halo, andthe like; and

Z is a non-ionizable moiety.

According to some of any of the embodiments of the present invention, Zis selected from hydrogen, alkyl, and a C(8-16)acyl.

According to some of any of the embodiments of the present invention,the silicon polyether is water-miscible.

According to some of any of the embodiments of the present invention,the mono-functional monomeric material (mono-functional monomer) is aUV-curable monomer.

According to some of any of the embodiments of the present invention,the mono-functional monomeric material (mono-functional monomer) isselected from the group consisting of an acrylate, a methacrylate, anacrylamide, a methacrylamide and a substituted vinyl monomer.

According to some of any of the embodiments of the present invention,the polyol is selected from the group consisting of Polyol 3165,polypropylene glycol, and polyglycerol; the mono-functional monomericmaterial is selected from the group consisting of an acrylate, amethacrylate, an acrylamide, a methacrylamide and a substituted vinylmonomer; and the silicone polyether is represented by Formula I, asdescribed herein in any of the respective embodiments.

According to some of any of the embodiments of the present invention, aconcentration of the mono-functional monomeric material (mono-functionalmonomer) ranges from 20 to 40 weight percents of the total weight of theformulation.

According to some of any of the embodiments of the present invention, aconcentration of the water-miscible polymeric material ranges from 40 to70 weight percents of the total weight of the formulation.

According to some of any of the embodiments of the present invention, aconcentration of the silicone polyether ranges from 5 to 20 weightpercents of the total weight of the formulation.

According to some of any of the embodiments of the present invention,the formulation further comprises an initiator.

According to some of any of the embodiments of the present invention,the formulation further comprises an additional agent, such as, but notlimited to, a surface active agent and/or an inhibitor.

According to an aspect of some embodiments of the present inventionthere is provided a method of fabricating a three-dimensional object,the method comprising dispensing a building material so as tosequentially form a plurality of layers in a configured patterncorresponding to the shape of the object, wherein the building materialcomprises a modeling material formulation and a support materialformulation, and wherein the support material formulation comprises theformulation as described herein in any of the embodiments thereof andany combination of these embodiments.

According to some of any of the embodiments of the present invention,the method further comprises, subsequent to the dispensing, exposing thebuilding material to curing energy, to thereby obtain a cured modelingmaterial and a cured support material.

According to some of any of the embodiments of the present invention,the method further comprises removing the cured support material, tothereby obtain the three-dimensional object.

According to some of any of the embodiments of the present invention,the removing comprises contacting the cured support material with water.

According to some of any of the embodiments of the present invention,the removing consists of contacting the cured support material withwater.

According to an aspect of some embodiments of the present inventionthere is provided a three-dimensional object fabricated by the method asdescribed herein in any one of the embodiments thereof and anycombination thereof.

According to some of any of the embodiments of the present invention,the object features characteristics as described herein.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

Implementation of the method and/or system of embodiments of theinvention can involve performing or completing selected tasks manually,automatically, or a combination thereof. Moreover, according to actualinstrumentation and equipment of embodiments of the method and/or systemof the invention, several selected tasks could be implemented byhardware, by software or by firmware or by a combination thereof usingan operating system.

For example, hardware for performing selected tasks according toembodiments of the invention could be implemented as a chip or acircuit. As software, selected tasks according to embodiments of theinvention could be implemented as a plurality of software instructionsbeing executed by a computer using any suitable operating system. In anexemplary embodiment of the invention, one or more tasks according toexemplary embodiments of method and/or system as described herein areperformed by a data processor, such as a computing platform forexecuting a plurality of instructions. Optionally, the data processorincludes a volatile memory for storing instructions and/or data and/or anon-volatile storage, for example, a magnetic hard-disk and/or removablemedia, for storing instructions and/or data. Optionally, a networkconnection is provided as well. A display and/or a user input devicesuch as a keyboard or mouse are optionally provided as well.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to additivemanufacturing (AM), and more particularly, but not exclusively, toformulations useful for forming a support material in additivemanufacturing such as three-dimensional inkjet printing, and to methodsof additive manufacturing utilizing same.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the Examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways.

A support material formulation for use in 3D inkjet printing shouldexhibit the following characteristics before curing: be liquid at roomtemperature; be dispensable by inkjet nozzles (e.g., exhibit a suitableviscosity at the working temperature); and have a UV reactivity suitablefor 3D printing.

After curing, the hardened (e.g., cured) support material shouldpreferably be characterized as being solid or semi-solid; and as beingsubstantially water-soluble. Preferably, the hardened support materialshould be readily removed by simple, automatable procedures, withoutapplying high temperature and/or harsh chemicals, so as to avoidpotential adverse effects to the final object.

Currently available water-soluble support materials for 3D inkjetprinting often fail to exhibit the required performance due to, forexample, material properties which do not meet the process and/orapparatus requirements, such as suitability for jetting via ink-jetnozzles, and/or mechanical strength sufficient to support the modelbeing formed; and, importantly, for not being easily removable from thefabricated object to provide a final object.

The present inventors have sought for support material formulationswhich would exhibit improved performance, particularly with regard toremoval of the support material from the model material.

More specifically, the present inventors have recognized that in orderto efficiently remove hardened support materials made of commonly usedformulations, such as UV-curable formulations, a prolonged preliminarydissolution in water (up to 17 hours) should be performed, followed by aprolonged treatment time in NaOH solution (3-8 hours), which by itselfis insufficient in case of thick model-support mix layer (as definedherein), and is often followed by immersion in glycerol aqueoussolution.

As discussed hereinabove, due to the aggressive processes involved inremoval of the support material, the mechanical properties of the modelmaterial may be adversely affected, and further, upon drying, residualglycerol is often present on the model material in case immersion inglycerol is required.

The present inventors have now designed and successfully prepared andpracticed novel support material formulations, which can easily andefficiently be removed by dissolution in water or an aqueous solution,without the need to use high temperatures and/or harsh chemicals. Thepresent inventors have shown that these novel formulations are usablefor forming a water-soluble hardened support material in 3D inkjetprinting methods, and exhibit improved performance compared to currentlyknown and/or available formulations for forming water-soluble hardenedsupport materials.

Herein throughout, the phrase “uncured building material” collectivelydescribes the materials that are dispensed during the fabricationprocess so as to sequentially form the layers, as described herein. Thisphrase encompasses uncured materials dispensed so as to form the object,namely, one or more uncured modeling material formulation(s), anduncured materials dispensed so as to form the support, namely uncuredsupport material formulations.

Herein throughout, the term “object” describes a final product of themanufacturing process. This term refers to the product obtained by amethod as described herein, after removal of the support material. The“object” therefore essentially consists of a cured modeling material,unless otherwise indicated.

The term “object” as used herein throughout refers to a whole object ora part thereof.

Herein throughout, the phrase “cured modeling material” or “hardenedmodeling material” describes the part of the building material thatforms the object, as defined herein, upon exposing the dispensedbuilding material to curing, and following removal of the cured supportmaterial. The cured modeling material can be a single cured material ora mixture of two or more cured materials, depending on the modelingmaterial formulations used in the method, as described herein.

Herein throughout, the phrase “modeling material formulation”, which isalso referred to herein interchangeably as “modeling formulation”,“model formulation” or simply as “formulation”, describes a part of theuncured building material which is dispensed so as to form the object,as described herein. The modeling formulation is an uncured modelingformulation, which, upon exposure to curing energy, forms the object ora part thereof.

An uncured building material can comprise one or more modelingformulations, and can be dispensed such that different parts of theobject are made upon curing from different modeling formulations, andhence are made of different cured modeling materials or differentmixtures of cured modeling materials.

Herein throughout, the phrase “hardened support material” is alsoreferred to herein interchangeably as “cured support material” or simplyas “support material” or “support” and describes the part of thebuilding material that is intended to support the fabricated objectduring the fabrication process, and which is removed once the process iscompleted and a hardened modeling material is obtained.

Herein throughout, the phrase “support material formulation”, which isalso referred to herein interchangeably as “support formulation” orsimply as “formulation”, describes a part of the uncured buildingmaterial which is dispensed so as to form the support material, asdescribed herein. The support material formulation is an uncuredformulation, which, upon exposure to curing energy, forms the hardenedsupport material.

Herein throughout, the term “water-miscible” describes a material whichis at least partially dissolvable or dispersible in water, that is, atleast 50% of the molecules move into the water upon contacting (e.g.,mixing) the material and water (e.g., contacting equal volumes orweights of the material and water).

Herein throughout, the term “water-soluble” describes a material thatwhen mixed with water in equal volumes or weights, a homogeneoussolution is formed.

Herein throughout, the term “water-dispersible” describes a materialthat forms a homogeneous dispersion when mixed with water in equalvolumes or weights.

Herein throughout, the phrase “dissolution rate” describes a rate atwhich an object is dissolved in a liquid medium. Dissolution rate can bedetermined, in the context of the present embodiments, by measuring thetime required for an object of a specific volume to completely dissolvein 1 liter or 500 ml of water, at room temperature, under continuousmagnetic stirring. The measured time is referred to herein as“dissolution time”.

Herein throughout, whenever the phrase “weight percents” is indicated inthe context of embodiments of a support material formulation, it ismeant weight percents of the total weight of the uncured supportmaterial formulation as described herein.

Herein throughout, some embodiments of the present invention aredescribed in the context of the additive manufacturing being a 3D inkjetprinting. However, other additive manufacturing processes, such as, butnot limited to, SLA and DLP, are contemplated.

The Support Material Formulation:

According to an aspect of some embodiments of the present inventionthere is provided a support material formulation, which comprises acurable, water-soluble mono-functional material; a non-curablewater-miscible polymeric material; and a silicone polyether.

Herein throughout, a “curable material” is a compound (monomeric oroligomeric compound) which, when exposed to curing energy, as describedherein, solidifies or hardens to form a cured modeling material asdefined herein. Curable materials are typically polymerizable materials,which undergo polymerization and/or cross-linking when exposed tosuitable energy source.

A “curable material” is also referred to herein and in the art as“reactive” material.

In some of any of the embodiments described herein, a curable materialis a photopolymerizable material, which polymerizes and/or undergoescross-linking upon exposure to radiation, as described herein, and insome embodiments the curable material is a UV-curable material, whichpolymerizes and/or undergoes cross-linking upon exposure to UV-visradiation, as described herein.

In some embodiments, a curable material as described herein is apolymerizable material that polymerizes via photo-induced radicalpolymerization.

In some of any of the embodiments described herein, a curable materialcan be a monomer, an oligomer or a short-chain polymer, each beingpolymerizable as described herein.

In some of any of the embodiments described herein, when a curablematerial is exposed to curing energy (e.g., radiation), it polymerizesby any one, or combination, of chain elongation and cross-linking.

In some of any of the embodiments described herein, a curable materialis a monomer or a mixture of monomers which can form a polymericmodeling material upon a polymerization reaction, when exposed to curingenergy at which the polymerization reaction occurs. Such curablematerials are also referred to herein as “monomeric curable materials”,or as “curable monomers”.

A curable material, e.g., a curable monomeric material (a curablemonomer), can be a mono-functional curable material or amulti-functional curable material.

In some of any of the embodiments described herein, the curable materialis a monomeric curable material and in some embodiments, it is amono-functional curable monomeric material (also referred to herein as“curable mono-functional monomer”).

Herein, a mono-functional curable material comprises one functionalgroup that can undergo polymerization when exposed to curing energy(e.g., radiation).

Herein, a multi-functional curable material comprises two or morefunctional groups that can undergo polymerization when exposed to curingenergy (e.g., radiation).

In some of any of the embodiments described herein, the curablemonomeric material is water-soluble or at least water-miscible, asdefined herein.

In some of any of the embodiments described herein, the curablemono-functional monomer comprises one or more hydrophilic substituents,which render it water soluble.

As used herein throughout, the term “hydrophilic” describes a physicalproperty of a compound or a portion of a compound (e.g., a chemicalgroup in a compound) which accounts for transient formation of bond(s)with water molecules, typically through hydrogen bonding.

A hydrophilic group is one that is typically charge-polarized andcapable of hydrogen bonding.

Hydrophilic groups typically include one or more electron-donatingheteroatoms which form strong hydrogen bonds with water molecules. Suchheteroatoms include, but are not limited to, oxygen and nitrogen.Preferably, a ratio of the number of carbon atoms to a number ofheteroatoms in a hydrophilic group is 10:1 or lower, and can be, forexample, 8:1, more preferably 7:1, 6:1, 5:1 or 4:1, or lower.

Hydrophilic groups are typically polar groups, comprising one or moreelectron-donating heteroatoms such as oxygen and nitrogen. Exemplaryhydrophilic groups include, but are not limited to, an electron-donatingheteroatom, a carboxylate, a thiocarboxylate, oxo (═O), a linear amide,hydroxy, a (C1-4)alkoxy, an (C1-4)alcohol, a heteroalicyclic (e.g.,having a ratio of carbon atoms or heteroatoms as defined herein), acyclic carboxylate such as lactone, a cyclic amide such as lactam, acarbamate, a thiocarbamate, a cyanurate, an isocyanurate, athiocyanurate, urea, thiourea, an alkylene glycol (e.g., ethylene glycolor propylene glycol), a phosphate, a phosphonate, a sulfate, asulfonate, sulfonamide, as these groups are defined herein, and anycombinations thereof (e.g., a hydrophilic group that comprises two ormore of the indicated hydrophilic groups).

A curable, water-soluble mono-functional material according to someembodiments of the present invention can be a vinyl-containing compoundrepresented by Formula I:

wherein at least one of R₁ and R₂ is

and/or comprises a hydrophilic group, as defined herein.

The (═CH₂) group in Formula I represents a polymerizable group, and istypically a UV-curable group, such that the material is a UV-curablematerial.

For example, R₁ is a hydrophilic group as defined herein and R₂ is anon-hydrophilic group, for example, hydrogen, C(1-4) alkyl, C(1-4)alkoxy, or any other substituent, as long as the compound iswater-soluble.

In some embodiments, R₁ is a carboxylate group, —C(═O)—OR′, and thecompound is a mono-functional acrylate monomer. In some of theseembodiments, R₂ is methyl, and the compound is mono-functionalmethacrylate monomer. In other embodiments, R₂ is a hydrophilicsubstituent, namely, a substituent which is, or which comprises, ahydrophilic group as described herein.

In some of any of these embodiments, the carboxylate group, —C(═O)—OR′,comprises R′ which is a hydrophilic group. Exemplary R′ groups include,but are not limited to, heteroalicyclic groups (having a ratio of 5:1 orlower of carbon atoms to electron-donating heteroatoms, such asmorpholine, tetrahydrofuran, oxalidine, and the likes), hydroxyl,C(1-4)alkyl optionally substituted or interrupted by one or morehydrophilic groups (e.g., hydroxy, —O—, amine or —NH—), hydroxy, thiol,alkylene glycol, or a hydrophilic polymeric or oligomeric moiety, asdescribed herein. An exemplary water soluble, mono-functional acrylatemonomer is acryloyl morpholine (ACMO). Another exemplary such monomer is[2-(acryloyloxy)ethyl]trimethylammonium chloride. Other water solubleacrylate or methacrylate mono-functional monomers are contemplated.

In some embodiments, R₁ is amide (—C(═O)—NR′R″), and the compound is amono-functional acrylamide monomer. In some of these embodiments, R₂ ismethyl, and the compound is mono-functional methacrylamide monomer. Insome of these embodiments, the amide is substituted. For example, one orboth of R′ and R″ in the amide group —C(═O)—NR′R″ is or comprises ahydrophilic group, as described herein for R′. Exemplary such monomersinclude N-(3,3-dimethylaminopropyl) methacrylamide, and methacrylamide(2-methyl-propenamide). Other water soluble acrylamide or methacrylamidemono-functional monomers are contemplated.

In some embodiments, one or both of R₁ and R₂ is/are a hydrophilic groupother than a carboxylate or an amide, as defined herein, for example, isa cyclic amide (lactam), a cyclic ester (lactone), a phosphate,phosphonate, sulfate, sulfonate, alkoxy, substituted alkoxy, or else, aslong as the monomer is water-soluble. In such embodiments, the monomeris a substituted vinyl monomer. Exemplary such vinyl monomers are vinylphosphonic acid and hydroxybutyl vinyl ether. Other water solublemono-functional vinyl ethers or otherwise substituted vinyl monomers arecontemplated.

In some of any of the embodiments described herein, the water-misciblepolymeric materials can be any of the water-miscible polymeric materialscommonly used in support material formulations.

In some of any of the embodiments described herein, the water-misciblepolymeric material is non-curable (also referred to herein as“non-reactive”). The term “non-curable” encompasses polymeric materialsthat are non-polymerizable under any conditions, as well as polymericmaterials that are non-curable under conditions at which themono-functional monomer as described herein is curable, or under anycondition used in a fabrication of the object. Such polymeric materialsare typically devoid of a polymerizable group or of aUV-photopolymerizable group.

In some embodiments, the polymeric material is non-reactive towards thecurable monomer as described herein, that is, it does not react with themonomer and is incapable of interfering with the curing of the monomer,under the fabrication conditions, including the curing conditions.

In some of any of the embodiments described herein the polymericmaterial is water soluble or water dispersible or water misciblepolymeric material, as defined herein.

In some embodiments, the polymeric material comprises a plurality ofhydrophilic groups as defined herein, either within the backbone chainof the polymer or as pendant groups. Exemplary such polymeric materialsare polyols. Some representative examples include, but are not limitedto, Polyol 3165, polypropylene glycol, polyethylene glycol, polyglycerol, ethoxylated forms of these polymers, paraffin oil and thelike, and any combination thereof.

In some of any of the embodiments described herein, the support materialformulation further comprises a water-miscible, non-curable,non-polymeric material, such as, for example, propane diol.

In some of any of the embodiments described herein, the support materialformulation as described herein comprises a silicone polyether.

Silicone polyethers are polymeric materials that typically comprise asilicone backbone and two or more polyether terminal and/or pendantgroups. The ratio of the silicone to polyether, and the molecular weightand composition of the components determine the solubility and specificproperties of a silicone polyether. When the polyether groups arependant groups, the silicone polyether is referred to as multi-pendantand when the polyether groups are terminal groups (attached to theterminal silicone backbone units of the silicone backbone), the siliconepolyether is referred to as linear di-functional polymer, or simply aslinear silicone polyether.

In some of any of the embodiments described herein, the siliconebackbone of a silicone polyether is of polydimethyl siloxane (PDMS,Dimethicone).

Silicone polyethers as described herein can be collectively representedby Formula I:

wherein:

n and m each independently an integer, such that n+m is an integer offrom 1 to 500, representing the number of backbone units in the siliconebackbone chain, minus 1 (the terminal unit which comprises B);

X is an alkylene, as defined herein or absent;

Y is a polyether moiety, as defined herein, or absent; and

A and B are each independently an alkyl or a polyether moiety, asdefined herein.

In some embodiments, A and B are each a polyether moiety, and X and Yare absent, such that the silicone polyether is a linear polymer.

In some embodiments, Y is a polyether moiety, optionally linked to thebackbone units via an alkylene (X), and the silicone polyether ismulti-pendant polymer. In some of these embodiments, A and B are eachindependently an alkyl, for example, methyl. Alternatively, one or bothof A and B is/are a polyether moiety, as defined herein.

It is noted that while the backbone units presented in Formula I are ofPDMS, the methyl substituents of some or all of the silicone backboneunits can be replaced by other substituents, for example, by an alkylother than methyl.

In some of any of the embodiments described herein, when A and B and/orY is a polyether moiety, this moiety can be the same or different. Thepolyether moieties can be collectively represented by Formula II:—O—[(CR′R″)x-O]y-Z   Formula II

wherein:

y is an integer of from 4 to 100, representing the number of repeatingalkylene glycol groups in the polyether moiety;

x is an integer of from 2 to 6, representing the number of carbon atomin each alkylene group;

R′ and R″ are each independently hydrogen, alkyl, cycloalkyl, halo,aldehyde, carbonyl, carboxylate, amine, and the like, or, alternatively,R′ and R″ can form together an oxo group, or a carbocyclic (aryl orcycloalkyl) or heterocyclic (heteroalicyclic or heteroaryl) group,representing optional substituents of some or all of the carbon atoms insome or all of the repeating alkylene groups in the polyether moiety;and

Z can be hydrogen, alkyl, acyl, aldehyde, amine, and the like, whichforms, together with the oxygen of the last alkylene glycol group, aterminal group of the polyether moiety.

A polyether moiety can therefore be composed of repeating alkyleneglycol backbone units, wherein the backbone units can be the same ordifferent (namely, 2 or more different types of alkylene glycol groups,which can be in any order in the polymeric moiety). When different, thealkylene glycol groups can differ from one another by the number ofcarbon atoms x and/or by the nature of R′ and/or R″.

In some of any of the embodiments described herein, the number ofalkylene glycol backbone units, y, ranges from 4 to 50, or from 4 to 30,or from 4 to 20, or from 4 to 10, including any subranges andintermediate values therebetween.

In some of any of the embodiments described herein, the polyether moietyis a polyethylene glycol moiety, such that for all alkylene glycolgroups, x is 2.

In some of these embodiments, all the alkylene glycol groups are thesame.

In some of these embodiments, all the alkylene glycol groups are thesame and are non-substituted, such that R′ and R″ are each hydrogen.

In some of these embodiments, some or all of the alkylene glycol groupsare substituted, for example, one or both carbon atoms in an alkylenegroup are substituted, as described hereinabove for R′ and/or R″ beingother than hydrogen.

In some embodiments, when the alkylene glycol is substituted, thesubstituent is a non-ionizable substituent, as defined herein.

In some embodiments, R′ and R″ are each independently hydrogen or alkyl.

In some embodiments, Z is a non-ionizable group, as described herein.

In exemplary embodiments, Z is hydrogen (forming a hydroxyl terminalgroup), alkyl (forming an alkoxy terminal group), or a C(8-16)acyl(forming an ester terminal group).

As used herein, the term “non-ionizable” means that a group or asubstituent is such that does not form an ion (a cation or an anion)spontaneously (namely, without applying a potential or withoutsubjecting it to chemical conditions which facilitate charge transfer).The term “non-ionizable” means, for example, that the group orsubstituent does not accept or donate a proton so as to turn into acation or an anion, respectively, in an aqueous solution of pH 7.

Examples of ionizable groups include, but are not limited to, amine,which forms ammonium cation, carboxylic acid, which forms carboxylateanion, sulfonic acid, which forms sulfonate anion, phosphonic orphosphoric acid, which forms phosphonate or phosphate anions, sulfuricacid, which forms sulfate anion, phosphine, which forms phosphiniumcation, sulfone, which forms sulfonium cation, pyridine, which formspyridinium cation and the like.

Groups such as alkyls, aryls, halo, cycloalkyls, esters, alkoxy,ketones, and the like are typically non-ionizable.

In some embodiments, at least some of all of the polyether moieties in asilicon polyether as described herein do not include an ionizablesubstituent or group. That is, when a polyether moiety comprises one ormore alkylene glycol group(s) that are substituted, the substituent isnon-ionizable, and/or Z forms a non-ionizable terminal group.

In some of any of the embodiments described herein, Z in Formula IIforms a terminal hydroxyl (when Z is hydrogen) or ester (when Z is acyl,—C(═O)—R′, with R′ as defined herein).

When Z is acyl, it can be, for example, a fatty acyl, such that R′ is analkyl being 4 to 16 carbon atoms in length. Alternatively, Z is an acylwhich is derived from other organic acids, such as, but not limited to,succinic acid, maleic acid, ascorbic acid and the like.

Alternatively, Z can be or can comprise a positively charged moiety suchas an ammonium moiety, e.g., quaternary ammonium.

In some of any of the embodiments described herein, when the siliconeether is multi-pendant, n and m are each independently an integer offrom 10 to 400, including any subranges and intermediate valuestherebetween.

In some of any of the embodiments described herein, when the siliconepolyether is multi-pendant, and the n to m ratio ranges from 10:1 to1:100, or from 1:1 to 1:100, including any subranges and intermediatevalues therebetween.

In some of any of the embodiments described herein, the siliconepolyether is characterized as water-soluble or water-dispersible at aconcentration of 10% by weight in water.

Exemplary such silicon polyethers are those marketed under the tradename“Silsurf” by SilTech, and include, for example, Silsurf A009-UP, Silsurf010-D, Silsurf C208, Silsurf J208, Silsurf D212-CG, Silsurf B608,Silsurf C410, Silsurf E608, Silsurf J1015-O, and Silsurf J1015-O-AC, andequivalent or analogous silicon ethers.

In some of any of the embodiments described herein, the type of thesilicone polyether (linear or multi-pendant), the ratio of n to m incase of a multi-pendant polymer, the molecular weight of the siliconepolyether, and the type of the polyether moiety, are selected such that(i) the silicone polyether is water miscible or water soluble; (ii) thesupport material formulation exhibits a desired viscosity at the working(e.g., jetting) temperature, as described herein; and (iii) the curedsupport material obtained from the formulation exhibits a desireddissolution rate, as described herein.

In some embodiments, the support material formulation is such that whena 20×20×20 mm cube is printed therefrom using a 3D printing system, andis placed in 1 Liter tap water, the cube is completely dissolved withinno more than 120 minutes, or no more than 100 minutes, or no more than90 minutes, or no more than 80 minutes, or no more than 75 minutes orthan 70 minutes. Shorter time periods are also contemplated.

Representative, non-limiting examples of silicone polyethers that areusable in the context of the present embodiments include the siliconepolyethers marketed as Silsurf C-410 and Silsense SW=12, by Siltechcompany, the structures of which are depicted in the Examples sectionthat follows.

Exemplary, non-limiting formulations according to some embodiments ofthe present invention are presented in Tables 1 and 2 in the Examplessection that follows.

In some of any of the embodiments described herein, a concentration ofthe curable, mono-functional monomer, as described herein in any of therespective embodiments, and any combination thereof, ranges from 20 to40 weight percents of the total weight of the formulation, including anyintermediate values and subranges therebetween.

In some of any of the embodiments described herein, a concentration ofthe water-miscible polymeric material, as described herein in any of therespective embodiments, and any combination thereof, ranges from 40 to70 weight percents of the total weight of the formulation, including anyintermediate values and subranges therebetween.

In some of any of the embodiments described herein, a concentration ofthe silicone polyether, as described herein in any of the respectiveembodiments, and any combination thereof, ranges from 5 to 20 weightpercents of the total weight of the formulation, including anyintermediate values and subranges therebetween.

Exemplary support material formulations according to some embodiments ofthe present invention comprise the following substances:

One or more curable water-soluble mono-functional monomer(s), asdescribed herein, at a concentration of from 20 to 40 weight percents ofthe total weight of the formulation, including any intermediate valuesand subranges therebetween;

One or more non-curable water miscible polymer(s), for example, one ormore polyol(s), as described herein, at a concentration of from 40 to 70weight percents of the total weight of the formulation, including anyintermediate values and subranges therebetween; and

One or more silicon polyether(s), as described herein, at aconcentration of 5 to 20 weight percents of the total weight of theformulation, including any intermediate values and subrangestherebetween.

In some of any of the embodiments described herein, and any combinationthereof, the support material formulation further comprises aninitiator, for inducing a polymerization of the curable material uponexposure to curing energy or curing conditions.

In some of these embodiments, the curable material is aphotopolymerizable or UV-curable material and the initiator is aphotoinitiator.

The photoinitiator can be a free radical photo-initiator, a cationicphoto-initiator, or any combination thereof.

A free radical photoinitiator may be any compound that produces a freeradical upon exposure to radiation such as ultraviolet or visibleradiation and thereby initiates a free-radical polymerization reaction.Non-limiting examples of suitable free-radical photoinitiators includephenyl ketones, such as alkyl/cycloalkyl phenyl ketones, benzophenones(aromatic ketones) such as benzophenone, methyl benzophenone, Michler'sketone and xanthones; acylphosphine oxide type photo-initiators such as2,4,6-trimethylbenzolydiphenyl phosphine oxide (TMPO),2,4,6-trimethylbenzoylethoxyphenyl phosphine oxide (TEPO), andbisacylphosphine oxides (BAPO's); benzoins and benzoin alkyl ethers suchas benzoin, benzoin methyl ether and benzoin isopropyl ether and thelike. Examples of photoinitiators are alpha-amino ketone, and1-hydroxycyclohexyl phenyl ketone (e.g., marketed as Igracure® 184).

A free-radical photo-initiator may be used alone or in combination witha co-initiator. Co-initiators are used with initiators that need asecond molecule to produce a radical that is active in the UV-systems.Benzophenone is an example of a photoinitiator that requires a secondmolecule, such as an amine, to produce a curable radical. Afterabsorbing radiation, benzophenone reacts with a ternary amine byhydrogen abstraction, to generate an alpha-amino radical which initiatespolymerization of acrylates. Non-limiting example of a class ofco-initiators are alkanolamines such as triethylamine,methyldiethanolamine and triethanolamine.

Free radical photoinitiators are usable when curable monomers whichpolymerize via free radical polymerization are included in theformulation. Such monomers include, for example, acrylates,methacrylates, acrylamides and methacrylamides, as described herein.Other curable monomers that undergo free radical polymerization whenexposed to light irradiation are contemplated.

Suitable cationic photoinitiators include, for example, compounds whichform aprotic acids or Bronstead acids upon exposure to ultravioletand/or visible light sufficient to initiate polymerization. Thephotoinitiator used may be a single compound, a mixture of two or moreactive compounds, or a combination of two or more different compounds,i.e. co-initiators. Non-limiting examples of suitable cationicphotoinitiators include aryldiazonium salts, diaryliodonium salts,triarylsulphonium salts, triarylselenonium salts and the like. Anexemplary cationic photoinitiator is a mixture of triarylsolfoniumhexafluoroantimonate salts.

Cationic photoinitiators are usable when curable monomers whichpolymerize via cationic polymerization are included in the formulation.

In some of any of the embodiments described herein, the uncured supportmaterial formulation may further comprise one or more additional agentsthat are beneficially used in the fabrication process. Such agentsinclude, for example, surface active agents, inhibitors and stabilizers.

In some embodiments, a support material formulation as described hereincomprises a surface active agent. A surface-active agent may be used toreduce the surface tension of the formulation to the value required forjetting or for other printing process, which is typically around 30dyne/cm. An exemplary such agent is a silicone surface additive such as,but not limited to, a surface agent marketed as BYK-345.

In some embodiments, a support material formulation as described hereinfurther comprises an inhibitor, which inhibits pre-polymerization of thecurable material during the fabrication process and before it issubjected to curing conditions. An exemplary stabilizer (inhibitor) isTris(N-nitroso-N-phenylhydroxylamine) Aluminum Salt (NPAL) (e.g., asmarketed under FirstCure® NPAL).

Suitable stabilizers include, for example, thermal stabilizers, whichstabilize the formulation at high temperatures.

According to some of any of the embodiments described herein, thesupport material formulation exhibits a viscosity that is suitable for3D inkjet printing.

In exemplary embodiments, the viscosity of the support materialformulation is lower than 30 cps, or lower than 25 cps, or lower than 20cps, at the working temperature. In some embodiments, the viscosity ofthe formulation is higher at room temperature and can be, for example,above 50 cps, or above 80 cps, at room temperature.

In some of any of the embodiments described herein, the support materialformulation is such that exhibits a viscosity of from 10 to 20 cps atroom temperature. In some embodiments, the curable monomer, thepolymeric material and particularly the silicone polyether, and theconcentration of each, are selected or manipulated such that theformulation exhibits a desired viscosity as described herein (beforecuring).

In some of any of the embodiments described herein, the support materialformulation is such that provides, upon exposure to curing conditions asdescribed herein, a cured support material that exhibits a dissolutiontime, as defined herein, of a 20×20×20 mm object, which is lower than120 minutes, lower than 100 minutes, lower than 90 minutes, lower than80 minutes and even lower than 75 minutes.

In some embodiments, the curable monomer, the polymeric material andparticularly the silicone polyether, and the concentration of each, areselected or manipulated such that the formulation provides a curedsupport material which exhibits such a dissolution time or acorresponding dissolution rate.

The Method:

According to an aspect of some embodiments of the present inventionthere is provided a method of fabricating a three-dimensional object,which utilizes a support material formulation as described herein. Themethod is also referred to herein as a fabrication process. In someembodiments, the method comprises dispensing an uncured buildingmaterial so as to sequentially form a plurality of layers in aconfigured pattern corresponding to the shape of the object. In someembodiments, the (uncured) building material comprises a modelingmaterial formulation and a support material formulation as describedherein in any of the respective embodiments and any combination thereof.

According to some embodiments of the present invention, the fabricationmethod is additive manufacturing of a three-dimensional object

According to some embodiments of this aspect, formation of each layer iseffected by dispensing at least one uncured building material, andexposing the dispensed building material to curing energy or curingconditions, to thereby form a cured building material, which iscomprised of a cured modeling material and a cured support material.

According to some of any of the embodiments described herein, theadditive manufacturing is preferably by three-dimensional inkjetprinting.

The method of the present embodiments manufactures three-dimensionalobjects in a layerwise manner by forming a plurality of layers in aconfigured pattern corresponding to the shape of the objects.

Each layer is formed by an additive manufacturing apparatus which scansa two-dimensional surface and patterns it. While scanning, the apparatusvisits a plurality of target locations on the two-dimensional layer orsurface, and decides, for each target location or a group of targetlocations, whether or not the target location or group of targetlocations is to be occupied by building material, and which type ofbuilding material (e.g., a modeling material formulation or a supportmaterial formulation) is to be delivered thereto. The decision is madeaccording to a computer image of the surface.

When the AM is by three-dimensional inkjet printing, an uncured buildingmaterial, as defined herein, is dispensed from a dispensing head havinga set of nozzles to deposit building material in layers on a supportingstructure. The AM apparatus thus dispenses (uncured) building materialin target locations which are to be occupied and leaves other targetlocations void. The apparatus typically includes a plurality ofdispensing heads, each of which can be configured to dispense adifferent building material. Thus, different target locations can beoccupied by different building materials (e.g., a modeling formulationand/or a support formulation, as defined herein).

In some of any of the embodiments of this aspect of the presentinvention, the method begins by receiving 3D printing data correspondingto the shape of the object. The data can be received, for example, froma host computer which transmits digital data pertaining to fabricationinstructions based on computer object data, e.g., in a form of aStandard Tessellation Language (STL) or a StereoLithography Contour(SLC) format, Virtual Reality Modeling Language (VRML), AdditiveManufacturing File (AMF) format, Drawing Exchange Format (DXF), PolygonFile Format (PLY) or any other format suitable for Computer-Aided Design(CAD).

Next, droplets of the uncured building material as described herein aredispensed in layers, on a receiving medium, using at least two differentmulti-nozzle inkjet printing heads, according to the printing data. Thereceiving medium can be a tray of a three-dimensional inkjet system or apreviously deposited layer. The uncured building material comprises asupport material formulation as described herein for any of therespective embodiments and any combination thereof.

In some embodiments of the present invention, the dispensing is effectedunder ambient environment.

Optionally, before being dispensed, the uncured building material, or apart thereof (e.g., one or more formulations of the building material),is heated, prior to being dispensed. These embodiments are particularlyuseful for uncured building material formulations having relatively highviscosity at the operation temperature of the working chamber of a 3Dinkjet printing system. The heating of the formulation(s) is preferablyto a temperature that allows jetting the respective formulation througha nozzle of a printing head of a 3D inkjet printing system. In someembodiments of the present invention, the heating is to a temperature atwhich the respective formulation exhibits a viscosity of no more than Xcentipoises, where X is about 30 centipoises, preferably about 25centipoises and more preferably about 20 centipoises, or 18 centipoises,or 16 centipoises, or 14 centipoises, or 12 centipoises, or 10centipoises.

The heating can be executed before loading the respective formulationinto the printing head of the 3D printing system, or while theformulation is in the printing head or while the composition passesthrough the nozzle of the printing head.

In some embodiments, the heating is executed before loading of therespective composition into the printing head, so as to avoid cloggingof the printing head by the composition in case its viscosity is toohigh.

In some embodiments, the heating is executed by heating the printingheads, at least while passing the first and/or second compositionthrough the nozzle of the printing head.

Once the uncured building material is dispensed on the receiving mediumaccording to the 3D printing data, the method optionally and preferablycontinues by exposing the dispensed building material to conditions theeffect curing. In some embodiments, the dispensed building material isexposed to curing energy by applying curing energy to the depositedlayers. Preferably, the curing is applied to each individual layerfollowing the deposition of the layer and prior to the deposition of theprevious layer.

The curing energy or condition can be, for example, a radiation, such asan ultraviolet or visible irradiation, or other electromagneticradiation, or electron beam radiation, depending on the buildingmaterial used. The curing energy or condition applied to the dispensedlayers serves for curing or solidifying or hardening the modelingmaterial formulation and the support material formulation. Preferably,the same curing energy or condition is applied to effect curing of boththe modeling materials and the support material. Alternatively,different curing energies or conditions are applied to the dispensedbuilding material, simultaneously or sequentially, to effect curing ofthe modeling material formulation and the support material formulation.

According to some of any of the embodiments of this aspect of thepresent invention, once the building material is dispensed to form anobject and curing energy or condition is applied, the cured supportmaterial is removed, to thereby obtain the final three-dimensionalobject.

According to some of any of the embodiments described herein, thesupport material is removed by contacting the cured support materialwith water or an aqueous solution. Contacting may be effected by meansknown in the art, for example, by immersing the object is water, and/orby jetting water onto the object. The contacting can be effectedmanually or in an automated manner.

In some of any of the embodiments described herein, removal of thesupport material is effected solely by (consists essentially of)contacting it with water. In some embodiments, the removal of the solidmaterial does not include further contacting the object with e.g.,basic/acidic aqueous solution and/or with glycerol, and does not includemechanical removal of the support material.

In some of any of the embodiments described herein, the contacting iseffected for a time period that is in correlation with the amount of thesupport material in the printed object. In some embodiments, thecontacting is effected for a time period of no more than 120 minutes, orno more than 100 minutes, or no more than 90 minutes, or no more than 80minutes, or no more than 75 minutes or no more than 70 minutes or nomore than 60 minutes. Shorter time periods are also contemplated.

In some embodiments, the contacting is effected during a time periodthat is shorter by at least 10%, at least 20%, at least 30%, at least40%, and even by 50%, or shorter, compared to a time period required toremove a cured support material made of commercially available orotherwise known support formulations.

Any system suitable for AM of an object is usable for executing themethod as described herein.

A representative and non-limiting example of a system suitable for AM ofan object according to some embodiments of the present inventioncomprises an additive manufacturing apparatus having a dispensing unitwhich comprises a plurality of dispensing heads. Each head preferablycomprises an array of one or more nozzles, through which a liquid(uncured) building material is dispensed.

Preferably, but not obligatorily, the AM apparatus is athree-dimensional inkjet printing apparatus, in which case thedispensing heads are inkjet printing heads, and the building material isdispensed via inkjet technology. This need not necessarily be the case,since, for some applications, it may not be necessary for the additivemanufacturing apparatus to employ three-dimensional printing techniques.Representative examples of additive manufacturing apparatus contemplatedaccording to various exemplary embodiments of the present inventioninclude, without limitation, binder jet powder based apparatus, fuseddeposition modeling apparatus and fused material deposition apparatus.

Each dispensing head is optionally and preferably fed via one or morebuilding material reservoir(s) which may optionally include atemperature control unit (e.g., a temperature sensor and/or a heatingdevice), and a material level sensor. To dispense the building material,a voltage signal is applied to the dispensing heads to selectivelydeposit droplets of material via the dispensing head nozzles, forexample, as in piezoelectric inkjet printing technology. The dispensingrate of each head depends on the number of nozzles, the type of nozzlesand the applied voltage signal rate (frequency). Such dispensing headsare known to those skilled in the art of solid freeform fabrication.

Optionally, but not obligatorily, the overall number of dispensingnozzles or nozzle arrays is selected such that half of the dispensingnozzles are designated to dispense support material formulations andhalf of the dispensing nozzles are designated to dispense modelingmaterial formulations, i.e. the number of nozzles jetting modelingmaterials is the same as the number of nozzles jetting support material.Yet it is to be understood that it is not intended to limit the scope ofthe present invention and that the number of modeling materialdepositing heads (modeling heads) and the number of support materialdepositing heads (support heads) may differ. Generally, the number ofmodeling heads, the number of support heads and the number of nozzles ineach respective head or head array are selected such as to provide apredetermined ratio, a, between the maximal dispensing rate of thesupport material and the maximal dispensing rate of modeling material.The value of the predetermined ratio, a, is preferably selected toensure that in each formed layer, the height of modeling material equalsthe height of support material. Typical values for a are from about 0.6to about 1.5.

For example, for a=1, the overall dispensing rate of support materialformulation is generally the same as the overall dispensing rate of themodeling material formulation(s) when all modeling heads and supportheads operate.

In a preferred embodiment, there are M modeling heads each having marrays of p nozzles, and S support heads each having s arrays of qnozzles such that M×m×p=S×s×q. Each of the M×m modeling arrays and S×ssupport arrays can be manufactured as a separate physical unit, whichcan be assembled and disassembled from the group of arrays. In thisembodiment, each such array optionally and preferably comprises atemperature control unit and a material level sensor of its own, andreceives an individually controlled voltage for its operation.

The AM apparatus can further comprise a curing unit which can compriseone or more sources of a curing energy or a curing condition. The curingsource can be, for example, a radiation source, such as an ultravioletor visible or infrared lamp, or other sources of electromagneticradiation, or electron beam source, depending on the modeling materialformulation(s) being used. The curing energy source serves for curing orsolidifying the building material formulation(s).

The dispensing head and curing energy source (e.g., radiation source)are preferably mounted in a frame or block which is preferably operativeto reciprocally move over a tray, which serves as the working surface (areceiving medium). In some embodiments of the present invention, thecuring energy (e.g., radiation) sources are mounted in the block suchthat they follow in the wake of the dispensing heads to at leastpartially cure or solidify the materials just dispensed by thedispensing heads. According to the common conventions, the tray ispositioned in the X-Y plane, and is preferably configured to movevertically (along the Z direction), typically downward. In variousexemplary embodiments of the invention, the AM apparatus furthercomprises one or more leveling devices, e.g. a roller, which serve tostraighten, level and/or establish a thickness of the newly formed layerprior to the formation of the successive layer thereon. The levelingdevice preferably comprises a waste collection device for collecting theexcess material generated during leveling. The waste collection devicemay comprise any mechanism that delivers the material to a waste tank orwaste cartridge.

In use, the dispensing heads as described herein move in a scanningdirection, which is referred to herein as the X direction, andselectively dispense building material in a predetermined configurationin the course of their passage over the tray. The building materialtypically comprises one or more types of support material formulationsand one or more types of modeling material formulations. The passage ofthe dispensing heads is followed by the curing of the modeling andsupport material formulation(s) by the source of curing energy orcondition (e.g., radiation). In the reverse passage of the heads, backto their starting point for the layer just deposited, an additionaldispensing of building material may be carried out, according topredetermined configuration. In the forward and/or reverse passages ofthe dispensing heads, the layer thus formed may be straightened by theleveling device, which preferably follows the path of the dispensingheads in their forward and/or reverse movement. Once the dispensingheads return to their starting point along the X direction, they maymove to another position along an indexing direction, referred to hereinas the Y direction, and continue to build the same layer by reciprocalmovement along the X direction. Alternatively, the dispensing heads maymove in the Y direction between forward and reverse movements or aftermore than one forward-reverse movement. The series of scans performed bythe dispensing heads to complete a single layer is referred to herein asa single scan cycle.

Once the layer is completed, the tray is lowered in the Z direction to apredetermined Z level, according to the desired thickness of the layersubsequently to be printed. The procedure is repeated to form athree-dimensional object which comprises a modeling material and asupport material in a layerwise manner.

In some embodiments, the tray may be displaced in the Z directionbetween forward and reverse passages of the dispensing head, within thelayer. Such Z displacement is carried out in order to cause contact ofthe leveling device with the surface in one direction and preventcontact in the other direction.

The system for performing the method as described herein optionally andpreferably comprises a building material supply apparatus whichcomprises the building material containers or cartridges and supplies aplurality of building material formulations (modeling materialformulation(s) and a support material formulation as described herein tothe fabrication apparatus.

The system may further comprise a control unit which controls thefabrication apparatus and optionally and preferably also the supplyapparatus as described herein. The control unit preferably communicateswith a data processor which transmits digital data pertaining tofabrication instructions based on computer object data, stored on acomputer readable medium, preferably a non-transitory medium, in a formof a Standard Tessellation Language (STL) format or any other formatsuch as, but not limited to, the aforementioned formats. Typically, thecontrol unit controls the voltage applied to each dispensing head ornozzle array and the temperature of the building material in therespective printing head.

Once the manufacturing data is loaded to the control unit, it canoperate without user intervention. In some embodiments, the control unitreceives additional input from the operator, e.g., using a dataprocessor or using a user interface communicating with the control unit.The user interface can be of any type known in the art, such as, but notlimited to, a keyboard, a touch screen and the like. For example, thecontrol unit can receive, as additional input, one or more buildingmaterial types and/or attributes, such as, but not limited to, color,characteristic distortion and/or transition temperature, viscosity,electrical property, magnetic property. Other attributes and groups ofattributes are also contemplated.

Further details on the principles and operations of an AM system such asdescribed herein is found in U.S. Patent Application having PublicationNo. 2013/0073068, the contents of which are hereby incorporated byreference.

According to some embodiments of each of the methods and systemsdescribed herein, the uncured building material comprises at least onesupport material formulation as described herein.

The Object:

According to an aspect of some embodiments of the present invention,there is provided a three-dimensional object prepared by the method asdescribed herein, in any of the embodiments thereof and any combinationthereof.

According to an aspect of some embodiments of the present inventionthere is provided a 3D object, fabricated by an AM method as describedherein.

According to some embodiments, the object is characterized by residualamount of a support material which ranges from null to no more than 10weight percents, or no more than 6 weight percents, or no more than 5weight percents, of the amount of the support material used in thefabrication process.

According to some embodiments, the object is devoid of a mixed layer, asdefined herein.

In some embodiments, the object is characterized as comprising a mixedlayer, as defined herein, which is no more than 10 volume percents, orno more than 8 volume percents, or no more than 6 volume percents, or nomore than 5 volume percents, or no more than 4 volume percents, or nomore than 3 volume percents, or no more than 2 volume percents or nomore than 1 volume percent of the total volume of the object.

According to some embodiments, the object is devoid of residual amountof glycerol.

By “devoid of” it is meant less than 0.1% by weight, or less than 0.05,or less than 0.01% by weight, or less, and up to nullified amount.

According to some embodiments, the object exhibits improved mechanicalproperties compared to objects made while using commercially availablesupport material formulations. Improved mechanical properties include,for example, higher tensile strength, higher elongation at break, lowerflexural modulus, higher flexural modulus, higher heat deformationtemperature (HDT), and higher notch impact. The improvement inmechanical properties can be, for example, of 10-100%, and even higher.Reference is made in this regard, for example, to Table 4 in theExamples section that follows.

As used herein the term “about” refers to ±10%.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of” means “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof. Throughout this application,various embodiments of this invention may be presented in a rangeformat. It should be understood that the description in range format ismerely for convenience and brevity and should not be construed as aninflexible limitation on the scope of the invention. Accordingly, thedescription of a range should be considered to have specificallydisclosed all the possible subranges as well as individual numericalvalues within that range. For example, description of a range such asfrom 1 to 6 should be considered to have specifically disclosedsubranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4,from 2 to 6, from 3 to 6 etc., as well as individual numbers within thatrange, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of thebreadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical, pharmacological, biological,biochemical and medical arts.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

As used herein, the term “amine” describes both a —NR′R″ group and a—NR′— group, wherein R′ and R″ are each independently hydrogen, alkyl,cycloalkyl, aryl, as these terms are defined hereinbelow.

The amine group can therefore be a primary amine, where both R′ and R″are hydrogen, a secondary amine, where R′ is hydrogen and R″ is alkyl,cycloalkyl or aryl, or a tertiary amine, where each of R′ and R″ isindependently alkyl, cycloalkyl or aryl.

Alternatively, R′ and R″ can each independently be hydroxyalkyl,trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl,heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate,hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano,nitro, azo, sulfonamide, carbonyl, C-carboxylate, O-carboxylate,N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate,O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine.

The term “alkyl” describes a saturated aliphatic hydrocarbon includingstraight chain and branched chain groups. Preferably, the alkyl grouphas 1 to 20 carbon atoms. Whenever a numerical range; e.g., “1-20”, isstated herein, it implies that the group, in this case the alkyl group,may contain 1 carbon atom, 2 carbon atoms, 3 carbon atoms, etc., up toand including 20 carbon atoms. More preferably, the alkyl is a mediumsize alkyl having 1 to 10 carbon atoms. Most preferably, unlessotherwise indicated, the alkyl is a lower alkyl having 1 to 4 carbonatoms (C(1-4) alkyl). The alkyl group may be substituted orunsubstituted. Substituted alkyl may have one or more substituents,whereby each substituent group can independently be, for example,hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl,heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine.

When an alkyl group connects two or more moieties via at least twocarbons in its chain, it is also referred to herein as “alkylene” or“alkylene chain”.

Alkene and Alkyne, as used herein, are an alkyl, as defined herein,which contains one or more double bond or triple bond, respectively.

The term “cycloalkyl” describes an all-carbon monocyclic ring or fusedrings (i.e., rings which share an adjacent pair of carbon atoms) groupwhere one or more of the rings does not have a completely conjugatedpi-electron system. Examples include, without limitation, cyclohexane,adamantine, norbornyl, isobornyl, and the like. The cycloalkyl group maybe substituted or unsubstituted. Substituted cycloalkyl may have one ormore substituents, whereby each substituent group can independently be,for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl,aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine.

The term “heteroalicyclic” describes a monocyclic or fused ring grouphaving in the ring(s) one or more atoms such as nitrogen, oxygen andsulfur. The rings may also have one or more double bonds. However, therings do not have a completely conjugated pi-electron system.Representative examples are piperidine, piperazine, tetrahydrofuran,tetrahydropyrane, morpholino, oxalidine, and the like. Theheteroalicyclic may be substituted or unsubstituted. Substitutedheteroalicyclic may have one or more substituents, whereby eachsubstituent group can independently be, for example, hydroxyalkyl,trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl,heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate,hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano,nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate,O-thiocarbamate, urea, thiourea, O-carbamate, N-carbamate, C-amide,N-amide, guanyl, guanidine and hydrazine.

A heteroalicyclic group which includes one or more of electron-donatingatoms such as nitrogen and oxygen, and in which a numeral ratio ofcarbon atoms to heteroatoms is 5:1 or lower, is included under thephrase “hydrophilic group” herein.

The term “aryl” describes an all-carbon monocyclic or fused-ringpolycyclic (i.e., rings which share adjacent pairs of carbon atoms)groups having a completely conjugated pi-electron system. The aryl groupmay be substituted or unsubstituted. Substituted aryl may have one ormore substituents, whereby each substituent group can independently be,for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl,aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine.

The term “heteroaryl” describes a monocyclic or fused ring (i.e., ringswhich share an adjacent pair of atoms) group having in the ring(s) oneor more atoms, such as, for example, nitrogen, oxygen and sulfur and, inaddition, having a completely conjugated pi-electron system. Examples,without limitation, of heteroaryl groups include pyrrole, furan,thiophene, imidazole, oxazole, thiazole, pyrazole, pyridine, pyrimidine,quinoline, isoquinoline and purine. The heteroaryl group may besubstituted or unsubstituted. Substituted heteroaryl may have one ormore substituents, whereby each substituent group can independently be,for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl,aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,O-carbamate, N-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine. Representative examples are pyridine, pyrrole, oxazole,indole, purine and the like.

The term “halide” and “halo” describes fluorine, chlorine, bromine oriodine.

The term “haloalkyl” describes an alkyl group as defined above, furthersubstituted by one or more halide.

The term “sulfate” describes a —O—S(═O)₂—OR′ group, or an —O—S(═O)₂—O—group, where R′ is as defined hereinabove.

The term “thiosulfate” describes a —O—S(═S)(═O)—OR′ group or a—O—S(═S)(═O)—O— group, where R′ is as defined hereinabove.

The term “sulfite” describes an —O—S(═O)—O—R′ group or a —O—S(═O)—O—group, where R′ is as defined hereinabove.

The term “thiosulfite” describes a —O—S(═S)—O—R′ group or an —O—S(═S)—O—group, where R′ is as defined hereinabove.

The term “sulfinate” describes a —S(═O)—OR′ group or an —S(═O)—O— group,where R′ is as defined hereinabove.

The term “sulfoxide” or “sulfinyl” describes a —S(═O)R′ group or an—S(═O)— group, where R′ is as defined hereinabove.

The term “sulfonate” describes a —S(═O)₂—R′ group or an —S(═O)₂— group,where R′ is as defined herein.

The term “S-sulfonamide” describes a —S(═O)₂—NR′R″ group or a—S(═O)₂—NR′— group, with R′ and R″ as defined herein.

The term “N-sulfonamide” describes an R'S(═O)₂—NR″— group or a—S(═O)₂—NR′— group, where R′ and R″ are as defined herein.

The term “sulfone” describes a —S—R′R″ group or —SR′— group, where R′and R″ are as defined herein.

The term “phosphonate” describes a —P(═O)(OR′)(OR″) group or a—P(═O)(OR′)(O)— group, with R′ and R″ as defined herein.

The term “thiophosphonate” describes a —P(═S)(OR′)(OR″) group or a—P(═S)(OR′)(O)— group, with R′ and R″ as defined herein.

The term “phosphinyl” or “phosphine” describes a —PR′R″ group or a —PR′—group, with R′ and R″ as defined hereinabove.

The term “phosphine oxide” describes a —P(═O)(R′)(R″) group or a—P(═O)(R′)— group, with R′ and R″ as defined herein.

The term “phosphine sulfide” describes a —P(═S)(R′)(R″) group or a—P(═S)(R′)— group, with R′ and R″ as defined herein.

The term “phosphate” describes an —O—PR′(═O)(OR″) group or an—O—PR′(═O)(O)— group, with R′ and R″ as defined herein.

The term “phosphonate” describes a —PR′(═O)(OR″) group or a PR′(═O)(O)—group, with R′ and R″ as defined herein.

The term “carbonyl” or “carbonate” as used herein, describes a —C(═O)—R′group or a —C(═O)— group, with R′ as defined herein.

The term “thiocarbonyl” as used herein, describes a —C(═S)—R′ group or a—C(═S)— group, with R′ as defined herein.

The term “oxo” as used herein, describes a (═O) group, wherein an oxygenatom is linked by a double bond to the atom (e.g., carbon atom) at theindicated position.

The term “thiooxo” as used herein, describes a (═S) group, wherein asulfur atom is linked by a double bond to the atom (e.g., carbon atom)at the indicated position.

The term “oxime” describes a ═N—OH group or a ═N—O— group.

The term “hydroxyl” describes a —OH group.

The term “alkoxy” describes both an —O-alkyl and an —O-cycloalkyl group,as defined herein.

The term “aryloxy” describes both an —O-aryl and an —O-heteroaryl group,as defined herein.

The term “thiohydroxy” describes a —SH group.

The term “thioalkoxy” describes both a —S-alkyl group, and a—S-cycloalkyl group, as defined herein.

The term “thioaryloxy” describes both a —S-aryl and a —S-heteroarylgroup, as defined herein.

The “hydroxyalkyl” is also referred to herein as “alcohol”, anddescribes an alkyl, as defined herein, substituted by a hydroxy group.

The term “cyano” describes a —C≡N group.

The term “cyanurate” describes a

group or

group, with R′ and R″ as defined herein.

The term “isocyanurate” describes a

group or a

group, with R′ and R″ as defined herein.

The term “thiocyanurate” describes a

group or

group, with R′ and R″ as defined herein.

The term “isocyanate” describes an —N═C═O group.

The term “isothiocyanate” describes an —N═C═S group.

The term “nitro” describes an —NO₂ group.

The term “acyl halide” describes a —(C═O)R″″ group wherein R″″ ishalide, as defined hereinabove.

The term “carboxylate” as used herein encompasses C-carboxylate andO-carboxylate.

The term “C-carboxylate” describes a —C(═O)—OR′ group or a —C(═O)—O—group, where R′ is as defined herein.

The term “O-carboxylate” describes a —OC(═O)R′ group or a —OC(═O)—group, where R′ is as defined herein. When R′ is other than H, this termdescribes an ester.

A carboxylate can be linear or cyclic. When cyclic, R′ and the carbonatom are linked together to form a ring, in C-carboxylate, and thisgroup is also referred to as lactone. Alternatively, R′ and O are linkedtogether to form a ring in O-carboxylate. Cyclic carboxylates canfunction as a linking group, for example, when an atom in the formedring is linked to another group.

The term “thiocarboxylate” as used herein encompasses C-thiocarboxylateand O-thiocarboxylate.

The term “C-thiocarboxylate” describes a —C(═S)—OR′ group or a —C(═S)—O—group, where R′ is as defined herein.

The term “O-thiocarboxylate” describes a —OC(═S)R′ group or a —OC(═S)—group, where R′ is as defined herein.

A thiocarboxylate can be linear or cyclic. When cyclic, R′ and thecarbon atom are linked together to form a ring, in C-thiocarboxylate,and this group is also referred to as thiolactone. Alternatively, R′ andO are linked together to form a ring in O-thiocarboxylate. Cyclicthiocarboxylates can function as a linking group, for example, when anatom in the formed ring is linked to another group.

The term “carbamate” as used herein encompasses N-carbamate andO-carbamate.

The term “N-carbamate” describes an R″OC(═O)—NR′— group or a—OC(═O)—NR′— group, with R′ and R″ as defined herein.

The term “O-carbamate” describes an —OC(═O)—NR′R″ group or an—OC(═O)—NR′— group, with R′ and R″ as defined herein.

A carbamate can be linear or cyclic. When cyclic, R′ and the carbon atomare linked together to form a ring, in O-carbamate. Alternatively, R′and O are linked together to form a ring in N-carbamate. Cycliccarbamates can function as a linking group, for example, when an atom inthe formed ring is linked to another group.

The term “carbamate” as used herein encompasses N-carbamate andO-carbamate.

The term “thiocarbamate” as used herein encompasses N-thiocarbamate andO-thiocarbamate.

The term “O-thiocarbamate” describes a —OC(═S)—NR′R″ group or a—OC(═S)—NR′— group, with R′ and R″ as defined herein.

The term “N-thiocarbamate” describes an R″OC(═S)NR′— group or a—OC(═S)NR′— group, with R′ and R″ as defined herein.

Thiocarbamates can be linear or cyclic, as described herein forcarbamates.

The term “dithiocarbamate” as used herein encompasses S-dithiocarbamateand N-dithiocarbamate.

The term “S-dithiocarbamate” describes a —SC(═S)—NR′R″ group or a—SC(═S)NR′— group, with R′ and R″ as defined herein.

The term “N-dithiocarbamate” describes an R″SC(═S)NR′— group or a—SC(═S)NR′— group, with R′ and R″ as defined herein.

The term “urea”, which is also referred to herein as “ureido”, describesa —NR′C(═O)—NR″R′″ group or a —NR′C(═O)—NR″— group, where R′ and R″ areas defined herein and R′″ is as defined herein for R′ and R″.

The term “thiourea”, which is also referred to herein as “thioureido”,describes a —NR′—C(═S)—NR″R′″ group or a —NR′—C(═S)—NR″— group, with R′,R″ and R′″ as defined herein.

The term “amide” as used herein encompasses C-amide and N-amide.

The term “C-amide” describes a —C(═O)—NR′R″ group or a —C(═O)—NR′—group, where R′ and R″ are as defined herein.

The term “N-amide” describes a R′C(═O)—NR″— group or a R′C(═O)—N— group,where R′ and R″ are as defined herein.

An amide can be linear or cyclic. When cyclic, R′ and the carbon atomare linked together to form a ring, in C-amide, and this group is alsoreferred to as lactam. Cyclic amides can function as a linking group,for example, when an atom in the formed ring is linked to another group.

The term “guanyl” describes a R′R″NC(═N)— group or a —R′NC(═N)— group,where R′ and R″ are as defined herein.

The term “guanidine” describes a —R′NC(═N)—NR″R′″ group or a—R′NC(═N)—NR″— group, where R′, R″ and R′″ are as defined herein.

The term “hydrazine” describes a —NR′—NR″R′″ group or a —NR′—NR″— group,with R′, R″, and R′″ as defined herein.

As used herein, the term “hydrazide” describes a —C(═O)—NR′—NR″R′″ groupor a —C(═O)—NR′—NR″— group, where R′, R″ and R′″ are as defined herein.

As used herein, the term “thiohydrazide” describes a —C(═S)—NR′—NR″R′″group or a —C(═S)—NR′—NR″— group, where R′, R″ and R′″ are as definedherein.

As used herein, the term “alkylene glycol” describes a—O—[(CR′R″)x-O]y-R′″ end group or a —O—[(CR′R″)_(z)—O]_(y)— linkinggroup, with R′, R″ and R′″ being as defined herein, and with z being aninteger of from 1 to 10, preferably, 2-6, more preferably 2 or 3, and ybeing an integer of 1 or more. Preferably R′ and R″ are both hydrogen.When z is 2 and y is 1, this group is ethylene glycol. When z is 3 and yis 1, this group is propylene glycol.

When y is greater than 4, the alkylene glycol is referred to herein aspoly(alkylene glycol). In some embodiments of the present invention, apoly(alkylene glycol) group or moiety can have from 10 to 200 repeatingalkylene glycol units, such that z is 10 to 200, preferably 10-100, morepreferably 10-50.

Various embodiments and aspects of the present invention as delineatedhereinabove and as claimed in the claims section below find experimentalsupport in the following examples.

EXAMPLES

Reference is now made to the following examples, which together with theabove descriptions illustrate some embodiments of the invention in a nonlimiting fashion.

Example 1

Table 1 below presents exemplary components which are usable forinclusion in a support material formulation according to someembodiments of the present invention

TABLE 1 # Component Trade name A ACMO ACMO B Hydroxybutyl vinyl etherHBVE C Alkoxylated polyol Polyol 3165 D Polypropylene glycol 2 kDaPluriol 2000 E Polypropylene glycol Pluriol 900 0.9 kDa F Propane diolPropane diol G Silicone polyether Silsurf C410 H Anionic/cationiccomplex Silplex CS-1 silicone polyether Coco I Polyglycerol R-PG3 JPhotoinitiator Irgacure ® 184 K Inhibitor NPAL L surface active agentBYK 345 M Water

Table 2 below describes exemplary support material formulations made ofvarious combinations of the materials presented in Table 1.

TABLE 2 Formu- Formu- Formu- Formu- Component lation 1 lation 2 lation 3lation 4 A X X X X B X C X D X X X E X X F X G X H X I X J X X X X K X XX X L X X X X M X X X X

Example 2

Different formulations containing a curable monomer, a water misciblepolymer and a water soluble or water miscible silicone polyether werecompared to a similar formulation containing Polyol 3165 instead of thesilicon polyether, in terms of viscosity and dissolution rate in water.

Viscosity of each of the tested formulations was determined beforecuring, at 75° C. A “suitable viscosity” ranges from 15-25 centipoise.

Dissolution rate was measured by placing 30 grams of the testedformulation in molds in UV oven. The cured material in the mold wasinserted into a beaker with 500 ml of water under continuous stirring.The time required to obtain complete dissolution of the material wasmeasured, and the dissolution rate was followed and measured.

The silicon polyethers marketed as AL-Sisurf C-410 and AL-Sisense SW-12(see, structures below), were found to exhibit the highest dissolutionrate and a viscosity similar to that of the Polyol 3165-containingformulation.

Other silicon polyether-containing formulations also exhibited similaror slightly higher viscosity and/or higher dissolution rate, compared tothe Polyol 3165-containing formulation. Generally, suitable viscosityand improved dissolution rate were observed for silicone polyetherswhich do not feature ionizable groups, as described herein.

Example 3

Dissolution rate of printed articles made of a support materialformulation according to some embodiments of the present invention ismeasured by printing the article, using solely the tested supportformulation, by a 3D inkjet printing system, placing the obtainedprinted article in a vessel containing tap water under continuousmagnetic stirring and monitoring the time required to completedissolution of the printed article. For comparison, commerciallyavailable support material formulation is used to form the same printedarticle, and its dissolution time under the same conditions is measured.

In an exemplary assay, 20×20×20 mm cubes are printed while using anexemplary support material formulation according to some embodiments ofthe present invention or a commercially available formulation, and theprinted cubes are subjected to curing by UV radiation. Each of the curedcubes is inserted into a beaker with 500 ml or 1 Liter of water undercontinuous stirring and the time to complete dissolution is monitored.

The time to complete dissolution of a cube made of a commerciallyavailable support material the time was 160 minutes, whereby the time tocomplete dissolution of a cube made using an exemplary support materialformulation according to some embodiments of the present invention islower.

Example 4

Objects were printed using a 3D inkjet printing system so as to havemodel walls surrounded by a support material.

Table 3 below presents dissolution times measured for objects ofvariable shapes, made using a modeling material formulation and anexemplary support material formulation according to some embodiments ofthe present invention (Soluble support II), upon curing, compared toobjects made of the same modeling formulation and a commerciallyavailable support material formulation (Soluble Support I), upon curing.

TABLE 3 Dissolution time Soluble Soluble Model Support Model Support IISupport I weight weight Dimensions Ball 1 h 12 min 2 h 30 min 69 grams29 grams 40 mm Pyramid 41 min 2 h 30 min 189 grams 192 grams 60 × 60 ×60 mm Thin walls 45 min 1 h 45 min 69 grams 60 grams 120 × 60 × 30 mmBuddha 1 h 39 min 3 h 45 min 147 grams 61 grams 51 × 80 × 45 mm Cow 1 h45 min 3 h 15 min 80 grams 45 grams 93 × 44 × 30 mm Mouse 3 h  3 h 45min 60 grams 92 grams 65 × 116 × 25 mm

As shown, a cured support material according to the present embodimentsexhibits dissolution times lower by 50% or more compared to a curedsupport material obtained using a representative commercially availablesupport material formulation.

The cured support material according to embodiments of the inventionexhibits significantly increased water solubility, as reflected by thesubstantially lower dissolution times.

Additional measurements, of mechanical and physical properties of theobjects upon removal of the support material, were performed and theobtained data is presented in Table 4. The data is presented so as toreflect the change of each property upon using the support formulationof the present embodiments (Soluble Support II) compared to SolubleSupport I formulation (for which the values are presented as “X”).

TABLE 4 Soluble Support I Soluble Support II Tensile Strength (MPa) X3X   Elongation at break (%) X 4X   Flexural Modulus (MPa) X 0.6XFlexural strength (MPa) X 3.7X HDT (° C.) X X Impact (printed notch)(J/m) X 1.3X

In additional assays, objects were printed using a 3D inkjet printingsystem so as to have model walls surrounded by a support material. Thesupport material was thereafter removed, and the object dried. The wallthickness was then measured with a micrometer device.

For objects with identical walls, an exemplary support materialaccording to some embodiments of the present invention or a commerciallyavailable support material formulation was used.

The cured support material made of an exemplary formulation according tosome embodiments of the present invention was removed using water, whilea cured support material made of a commercially available supportmaterial formulation required at least a following treatment in acaustic solution (e.g. 1% NaOH) to receive similar results.

After removal of the support material measurements are made fordetermining the presence and properties of a mixed layer, as definedherein.

In some embodiments, measurements are made by determining a thickness ofa mixed layer, and estimating the volume percent of the mixed layerrelative to the printed object's volume. In an exemplary assay, anobject having a cube shape is printed using a modeling material andsupport material formulations, and the volume percent of the mixed layeris determined according to the following equation:% mixing layer=(mixing layer thickness)×(surface area of cube)/volume ofcube

A 1 cm³ cube printed using a commercially available formulationtypically comprises at least 6%, and even 10% of a mixed layer. The samecube printed with a support material formulation according toembodiments of the present invention comprises a mixed layer at a volumepercent of less than 10%, or less than 6%, or less than 5%, or less than4%, or even less.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting. In addition, any priority document(s) of this applicationis/are hereby incorporated herein by reference in its/their entirety.

What is claimed is:
 1. A support material formulation comprising: acurable, water-soluble mono-functional monomeric material of theformula:

wherein: R₁ is —C(═O)—OR′ and R′ is a hydrophilic group selected from aheteroalicyclic group having a ratio of 5:1 or lower of carbon atoms toelectron-donating heteroatoms, C(1-4)alkyl optionally substituted orinterrupted by one or more of hydroxy, —O—, amine or —NH—, hydroxy,thiol, and alkylene glycol, or R₁ is —C(═O)—NR′R″, and R′ and R″ areeach independently selected from hydrogen, alkyl, cycloalkyl, aryl,hydroxyalkyl, trihaloalkyl, a heteroaryl, and a heteroalicyclic,provided that at least one of R′ and R″ is a hydrophilic group selectedfrom a heteroalicyclic group having a ratio of 5:1 or lower of carbonatoms to electron-donating heteroatoms, C(1-4)alkyl optionallysubstituted or interrupted by one or more of hydroxy, —O—, amine or—NH—, and alkylene glycol; and R₂ is selected from hydrogen, C(1-4)alkyl, and C(1-4) alkoxy, a non-curable water-miscible polymericmaterial selected from an alkoxylated polyol, polypropylene glycol, andpolyglycerol, and a silicone polyether having a polydimethyl siloxanebackbone and two or more polyether terminal and/or pendant groups,wherein: a concentration of said mono-functional monomeric materialranges from 20 to 40 weight percent of the total weight of theformulation, a concentration of said water-miscible polymeric materialranges from 40 to 70 weight percent of the total weight of theformulation, and a concentration of said silicone polyether ranges from5 to 20 weight percent of the total weight of the formulation.
 2. Theformulation of claim 1, wherein R₁ is —C(═O)—OR′.
 3. The formulation ofclaim 2, wherein R′ is said heteroalicyclic group.
 4. The formulation ofclaim 1, wherein said a curable, water-soluble mono-functional monomericmaterial is selected from acryloyl morpholino,[2-(acryloyloxy)ethyl]trimethylammonium chloride,N-(3,3-dimethylaminopropyl) methacrylamide, and methacrylamide(2-methyl-propenamide).
 5. The formulation of claim 1, wherein saidwater-miscible polymeric material comprises a polypropylene glycol. 6.The formulation of claim 4, wherein said water-miscible polymericmaterial comprises a polypropylene glycol.
 7. The formulation of claim1, wherein said silicone polyether is represented by Formula I:

wherein: n and m each independently an integer, wherein n+m is aninteger of from 1 to 500, representing the number of backbone units,minus 1; X is an alkylene or absent; Y is said polyether moiety orabsent; and A and B are each independently an alkyl or said polyethermoiety, provided that either Y or each of A and B is said polyethermoiety, wherein when X is said alkylene, Y is said polyether moiety. 8.The formulation of claim 7, wherein said polyether moiety is representedby Formula II:—O—[(CR′R″)x-O]y-Z   Formula II wherein: y is an integer of from 4 to100; x is an integer of from 2 to 6; R′ and R″ are each independentlyhydrogen, alkyl, cycloalkyl, halo, and the like; and Z is anon-ionizable moiety.
 9. The formulation of claim 8, wherein Z isselected from hydrogen, alkyl, and a C(8-16)acyl.
 10. The formulation ofclaim 1, further comprising an initiator.
 11. The formulation of claim1, further comprising a surface active agent and/or an inhibitor.
 12. Amethod of fabricating a three-dimensional object, the method comprisingdispensing a building material so as to sequentially form a plurality oflayers in a configured pattern corresponding to the shape of the object,wherein said building material comprises a modeling material formulationand a support material formulation, and wherein said support materialformulation comprises the formulation of claim
 1. 13. The method ofclaim 12, further comprising, subsequent to said dispensing, exposingthe building material to curing energy, to thereby obtain a curedmodeling material and a cured support material.
 14. The method of claim13, further comprising removing said cured support material, to therebyobtain the three-dimensional object.
 15. The method of claim 14, whereinsaid removing comprises contacting said cured support material withwater.
 16. The method of claim 14, wherein said removing consists ofcontacting said cured support material with water.
 17. Athree-dimensional object fabricated by the method of claim 12.